I am sorry for your loss. I doubt the shepherds were strays. I know a lot of people who actually feed thiers raw meet because it is easier to just let them lose when they go on vacation. This way the dog has the instict to hunt for food and is use to the raw meat. I told those people they were well butt holes, well I used different words LOL. I am going to put electric fencing around my pens so if this happens to me at least the predator will get zapped before he tries to do damage. Again I am sorry but all we can do is learn, fix and move forward. It hurts but it will make you stronger and the other flocks need you now.